Propeller for surface water craft



May 14, 1929. w J o 1,713,448

PROPELLER FOR SURFACE WATER CRAFT Filed June 2, 1928 V/fl ATTORNEY Patented May 14, 1929.

UNITED STATES WILLIAM J'. BOE, OI' NEWBURGH, NEW YORK. i

PBPELLER FOR SUBFACE WATER CBAI'T.

Application filed ,Tune 2,

This invention relates to a propelling means for what may be termed surface watercraft, such as hydroplanes or the like, which craft when their maximum speed is attaned have such a shallow draft as to practically skim or glide over the surface of the Water.

' In craftof this nature where it is desirable, in order to obtain the maximum speed possible, for eliminating resistance oflered by the use of the rudder for counteractmg the tendency of a single propeller to swerve the craft laterally from a true course, separate propellers turning in opposite directions have been employed, the same being either driven by separate power plants or by the same power plant through the medium of suitable gearing or other connection. In the former instance, where separate power plants are employed for each propeller, it has been found that there is invariably a 'difference in the thrust produced which necessitates counter-action by the use of the rudder, while in the latter case the friction encountered by the use of gearing or other means of connection more than neutralizes the advantage sought to be gained.

In my prior United States Letters Patent No. 1555338, a double crank shaft motor was devised for the purpose of overcoming the above recited defects and disadvantages, but due to the diameter and Construction of the propellers, a wide spacing of the same was necessitated which obviously disposed the axis of each blade at a considerable angle to the path of travel of the craft, thereby materially reducing the efliciency of the thrust, in addition to requiring an unnecessary angular disposition of the connecting rods or making the connecting rods inconveniently long.

The present invention, therefore, aims to further solve the problem by virtue of an improved re-designed set of propellers which are so constructed that the blades and shafts nest together in such close proximity that they are practically disposed parallel to the path of travel of the craft.

A further advantage flowing from the Construction of the propellers which permits of their arrangement in close proximity to each other is the permission of the use of synchronizing gears of diameters comparatively smaller than the diameters of the propellers so as to allow the lower part of the propellers to extend below the bottom line 1928. Serial No. 282390.`

of the craft and at the same time permitting the shafts to be disposed in a horizontal plane resulting in the most effective thrust. 1th the above recited and other objects' in view, reference is had to the' following description and accom an in drawi s in which there is exhibite d mie zam e mbodiment of the invention, while the claims define the actual scope of the same.

In the drawings:

Figure 1 is a sectional plan view throu h the stern of a boat equipped with a propel er means constructed in accordance with the invention.

Figura 2 is a longitudinal sectional view taken approximately on the line 2 2 of Figure 1.

Figure 3 is a transverse sectional View taken approximately on the line indicated at 3-3 in Figure 1.

Referring to the drawings by characters of reference, 5 designates a surface craft which is formed at the stern with a recess 6 open at the bottom to aflord a compartment within which' the propulsion means is disposed. As previously set forth, the craft or' boat is of that type which has a very shallow draft when the same attains its maximum speed. The propelling means which constitutes the subject matter of the present invention includes a pair of propellers 7 and 8, each of which includes a shaft 9 of spiral or helical formation and a similarly formed blade 10. Both the shaft and blade have slightly more than a complete turn or approximately one turn and a half. The portions 11 of the blade exceeding the complete turn are at the leading end and are tapered off and merged into the shaft for the purpose of warding ofl' obstructions which may be encountered, to prevent damage to the struc ture and to cause the blades to enter the water more freely. In practice, the propellers 7 and 8 ar'e turned or rotated in opposite' directions and the spiral blades and shafts of each propeller are closely nested due to their structure so that the shafts may be arranged in approximately a parallel relation to each other and to the path of movement of the craft. It thus follows that their motion may be synchronized by means v of gears 12 and 13 disposed within the hull of the boat 'while the lower part of the propellers may extend below the bottom line of the boat without being inclined whereb maximum thrust efliciency may be obtaine The propellers are arranged in side by side r'elation and are dis'posed With respect to the surface of the water When the o'aft attains its maximum speed Whereby only the lower portons of the blades are actually submerged. i r

From the foregoing construction and arrangement, it is obvious that a propulson means for surface craft has been devised which prevents later-al swerving of the craft and tends to drive the same in a true course speed Q S, a pair of oppositely driven propellers having oppositely spir'aled shafts and blades disposed in nesting relation.

2. In a propelling means for surface speed beats, a pair of ,oppostely driven propellers having oppostel'y spiraled shafts and blades disposed in riesting relation and each mounted on a horizontal axis in such a manner as to dispose only the lower part of each blade in the Water When theboat attains its maximum speed' 3. In a propelling means for surface Watercraft, a pair of oppositely driven propellers having oppositely spiraled' internested shafts and blades.

WILLIAM J ROE. 

